If you prefer the popup to be shown only once for a visitor, then you can use the cookie time setting to specify a time in hours that will prevent the popup from showing again to a particular visitor.
There is no limit on the number of hours. For example if you want to prevent the popup from showing for 30 days then you can specify 720 hours.
If you don't want to use the cookie function, then leave the number of hours as 0.